[Netalyzr] intranet proxy detection gets web server instead of proxy

I have a machine with a squid proxy (port 3123) and a web server (port
80) running in my intranet. The proxy configuration for my machine is
distributed with a proxy.pac file. This way, my browser contacts the
intranet proxy, which contacts remote web servers directly.
With this configuration, netalyzr detects a wrong proxy in my intranet.
It probes the correct machine but misinterprets the apache web server on
port 80 als proxy, which is not configured as proxy. I removed the
mod_proxy.so and corresponding modules from httpd.conf, so it really
cannot. This results in wrong reports from netalyzr that a proxy alters
responses and performs broken caching.
This is an excerpt from the client logfile:
009,582 test-7| Starting checkURL
009,687 test-7| Response code 200
009,689 test-7| Global client addr via HTTP is 130.180.63.129
009,689 test-7| Suspecting proxy at linux1.wombaz.localnet:80, verifying.
009,691 test-7| connected to 'linux1.wombaz.localnet/10.10.10.11:80' in 1 ms
009,697 test-7| read response headers in 6 ms
009,697 test-7| HTTP headers received: Date Server Content-Length Connection Content-Type
009,697 test-7| Connection header is close
009,697 test-7| Content length is: 339
009,697 test-7| Got all content
009,697 test-7| Proxy confirmed via ID string in payload.
According to proxy.pac, the proxy runs on linux1.wombaz.localnet:3128,
and according to the X-Cache-Lookup header applications could be able to
determine the correct port 3128 even without proxy.pac.
If I manually configure the browser (Firefox) to directly connect to
websites, no proxy is detected - which is fine.
This is the link for the session with proxy autoconfiguration file:
http://netalyzr.icsi.berkeley.edu/restore/id=ae81b058-31561-8df8f214-2702-41dc-b85d
using the cli version, netalyzr doesn't detect any proxy (which is fine):
http://netalyzr.icsi.berkeley.edu/restore/id=43ca253f-13251-c562e872-9d42-4b5e-a6f6
Tschau
Alex